1. Field of the Invention
The invention relates generally to gas springs and like devices and particularly to improved devices of the piston-and-cylinder type in which the piston rod may be locked automatically at one end of its stroke against a force tending to expel the piston rod.
2. The Prior Art
Gas springs, which are devices of the type described, are employed between the body of a motor car or like vehicle and a cover, such as a hood, trunk lid, or door mounted on the body for movement about a horizontal axis. The fluid pressure in the spring tends to move the piston in a direction to expel the piston rod from the cylinder cavity and thereby to move the cover in an upward direction, whereby little or no manual effort is needed for lifting the cover. For downward movement of the cover, only the difference between the forces exerted on the cover by gravity and by the gas in the spring need to be overcome by hand. It is known to equip such gas springs with devices which impede movement of the piston rod from one of its axially terminal positions and thereby hold the cover in a lowermost angular position against the force of the gas in the spring independently of a latch or lock securing the cover directly to the vehicle body. In our earlier applications Ser. No. 938,228 now abandoned and Ser. No. 791,011, now U.S. Pat. No. 4,166,612 we have disclosed gas springs equipped with improved devices for accomplishing this function in a new and advantageous manner.
The present application is directed to the subject matter of our prior application Ser. No. 938,228 and to still further improvements therein having utility in gas springs and other devices of the piston-and-cylinder type referred to.